Did You Know!
Your Eyes Can Detect a Single Photon of Light
The human eye is far more sensitive than most people realize. Under ideal dark conditions, the retina can detect just a single photon—the smallest measurable unit of light.
Specialized cells called rod cells are responsible for this incredible sensitivity. These cells allow humans to see in extremely low-light environments, which is why your eyes slowly adjust when you walk into a dark room.
Scientists believe the human visual system evolved this sensitivity to help early humans detect movement and threats at night.
